FIG. 1 illustrates a front view of a prior art wiring device intended for mounting in a standard electrical box. The device of FIG. 1 includes a molded plastic body having a face 10 that may include any type of electrical interface. The example of FIG. 1 includes two receptacles (a duplex receptacle), but other examples include switches, dimmers, fan speed controls, occupancy sensors, etc. A wiring device typically includes a metallic strap that is used to mount the device in an electrical box. In the example of FIG. 1, two mounting portions 12 of the strap are visible. Each mounting portion includes an elongated hole 14. The wiring device is attached to the electrical box with two mounting screws that are passed through the mounting holes 14 and screwed into threaded holes in the electrical box.
The front face of the electrical box is typically flush with, or slightly recessed from, the face of the building materials that form the wall, floor or ceiling in which the box is mounted. Therefore, mounting ears or tabs 16 are included to keep the mounting portion of the strap flush with the building materials when the wiring device is attached to the electrical box.
The elongated holes 14 allow the position of the wiring device to be adjusted horizontally as shown by arrow 18, and to a lesser extent, vertically as shown by arrow 20 before the mounting screws are tightened down. The mounting holes 14 also enable the wiring device to rotate to a certain extent as shown by arrow 22. After the wiring device is attached to the electrical box, and its position adjusted, a wall plate is attached with screws that thread into wall plate mounting holes 24. The wall plate has an opening that is the same shape as the face 10 of the wiring device, and slightly larger so the face can fit within the opening.
In a multi-gang installation, two or more wiring devices are installed side-by-side in an electrical box. The three different types of adjustment make it difficult to maintain the relative alignment, i.e., horizontal spacing, rotation, vertical position, etc., of the devices so that their faces fit within the adjacent openings of a multi-gang wall plate. One prior art solution to the alignment problem involves the use of an alignment tool that holds the devices in the proper position while the installer tightens the mounting screws. The tool is then removed before the wall plate is installed. Another solution involves the use of a separate alignment plate that is attached to the wall first. Special holes on the wiring devices are aligned with pegs on the alignment plate which remains attached to the wall and becomes part of the installation.